With the constantly expansion of information technology and computer market, electrical products grow rapidly in the tendency toward smaller size, faster speed and more functions. Nowadays for the mass development of wireless device and the demand for wireless communication, the wireless modules are embedded in many advanced electrical devices, such as wireless keyboard, wireless mouse, etc. Therefore, the wireless transmitter and receiver become increasingly important. Transmission through radio or infrared rays both requires the wireless transmitter and receiver for executing signal transmitting and receiving.
Ordinary laptop or notebook both use PCMCIA card, according to the standard made by Personal Computer Memory Card International Association, and the card is usually inserted into the slot of computer. Presently the modem card and network card using PCMCIA interface is available. PCMCIA modem cards, being applied to receive data from and transmit data to the remote, have become widespread and popular computer equipment. Those who are familiar with the ordinary skills would appreciate that modem is capable of encoding binary signal information into analogy signal one.
Wireless network benefits to mobile operating staff and ISP, that is, this technology would provide significant advantage for business. In specific area, such as conference room, hotel lobby, Internet coffee shop and so on, this wireless technology could be applied to provide service of wireless communication and broadband network, hence beneficial both for user and provider. Besides, the identity recognition module could be applied to recognize the user and keep one's bill for the sake of convenience.
In view of the consideration mentioned, the security of usage gets increasingly important. Applying secret code and identification technique could help preventing the leak of data or confidentiality and recognizing the user for keeping account.
There is a subscriber identity module (SIM) which is applied in popular mobile phone system, such as GSM, DCS, PCS. Its major function is assuring the identification for the demand of the linkage between the mobile communication device and network, and locating the user. The information provided by SIM card includes user code, user identity, and security password.